Move DateFormat.zeroPad() back to upstream.

We can only safely use TextUtils.formatSimple() when formatting
strings that don't appear in UI, since locales can use different
glyphs for representing numerals.

Bug: 174576537
Test: manual
Exempt-From-Owner-Approval: revert
Change-Id: Iafba1ccde239e3053b2a462c3d0c248795fbf5fc

core/java/android/text/format/DateFormat.java

@@ -698,7 +698,7 @@ public class DateFormat {
     }
 
     private static String zeroPad(int inValue, int inMinDigits) {
-        return TextUtils.formatSimple("%0" + inMinDigits + "d", inValue);
+        return String.format(Locale.getDefault(), "%0" + inMinDigits + "d", inValue);
     }
 
     /**